1. Field of the Invention
The present invention relates to a process for the treatment of objects with an inflammable volatile liquid.
2. Decription of the Related Art
The industrial cleaning by immersion of objects to be treated in a solvent has been known for a long time. The advent of noninflammable solvents, such as halogenated hydrocarbons (particularly chlorofluorocarbons or CFC) has been considered for several decades as a very major progress because it overcomes the risk of fire or explosion. For ecological regions, unfortunately, these products are now prohibited, and it is necessary to return to older solvents, and to take other precautions to limit the risk of fire.
The present invention is directed toward the use of cleaning products of class "A3"which is to say products whose flash point is between 55.degree. and 100.degree. C.
In normal operation, the proximity of a hot point and a flame in the environment of a cleaning machine using these products gives rise to a serious risk of fire or deflagration.
In the presence of an accidental escape, the solvent dissipates outside the tank, exposing the environment of the machine to the same risks, even if the hot point or the flame is at a substantially greater distance from the machine. It is possible to place a tank containing the dangerous product within a closed chamber, and to establish in this chamber a nonoxidizing protective atmosphere, which is to say containing for example less than 5% oxygen. The treatment operations would take place within this chamber, and once they were completed, the dangerous liquid would be transferred to a separate closed receptacle.
The opening of the chamber, for withdrawing the treated products, could not be performed without precautions, because the protective atmosphere is charged with solvent vapors, whose mixture with ambient air could create dangerous conditions.
It is known to overcome such problems with a gas lock.
Another solution of this problem can consist in interposing, at the inlet and outlet of the chamber, a "condensation chamber", provided with a condenser maintained at a fairly low temperature to reduce the content of the solvent vapors in the atmosphere to a fairly low level to avoid any risk of combustion. The passage through the condensation chamber of the products leaving the chamber must be slow to permit the vaporization of at least the major part of the solvent which remains on the surface of the objects, and if desired of their support or a basket which serves to move them. The condensation chamber located at the outlet thus constitutes also a "drying chamber", forming a part of the enclosure.
On the other hand, the movement of the objects in the condensation chamber, at the inlet as at the outlet, should be fairly slow to avoid the appearance of eddies which could place the ambient air in contact with the gas charged with solvent vapors, either within the chamber or outside of it.
These various precautions require that the speeds of movement within the treatment installation are often very much less than those which can be achieved in a manufacturing or packaging station, which complicates considerably the design of these plants.
The drying, which is the principal component of the slowness, can be accelerated if the last treatment stage consists in a passage through a tank containing water, deionized if desired, or another noninflammable liquid, because the drying can then be executed by blowing hot air, outside the chamber with the protective atmosphere.
However, this solution cannot be used in all cases. Moreover, it increases the complexity of the treatment installation because the first treatment liquid must be separated from the second liquid formed by the water or a noninflammable liquid.
The applicant has moreover determined that among the solvents envisioned for the replacement of halogenated hydrocarbons, certain ones (such as CFC) are sensitive to the presence of water vapor in the surrounding atmosphere, and undergo changed effectiveness by this presence, particularly in the case of operation in a closed circuit.